The present invention relates to a dye-labeled protein conjugate prepared by binding an antibody to a protein to form a protein complex or conjugate and labelling the conjugate with a cyanine dye, and further to a method for preparing the same.
The dye-labeled antibody, which is obtained by labeling an antibody with a dye, specifically reacts with an antigen included in a sample solution and is readily recognizable with naked eyes. The dye-labeled antibodies are accordingly applied for immunosensors, each of which takes advantage of an immunological antigen-antibody reaction to detect a target substance included in a sample solution, and are used for diagnoses in a variety of medical institutions.
Cyanine dyes having the high molar absorption coefficient and the high reactivity are often used to label antibodies (Bioconjugate Chemistry Vol. 4, No. 2, pp105-111, 1993).
The functional group of the cyanine dye reacts with and is covalently bound to an amino group or a carboxyl group included in an antibody, and 20 to 50 molecules of the dye are attached to one molecule of the antibody.
The cyanine dye-labeled antibody thus prepared generally has high visual recognizability, and is effectively applied for, for example, immunochromatography to detect a small amount of a specific substance, such as human chorionic gonadotropin (HCG) that is present only in the urine of pregnant women.
The antibody generally includes several hundreds to several thousands of amino group or carboxyl group. The antibody has a three-dimensional steric configuration and thereby has only 50 groups that are related to the reaction. Namely only 50 molecules of the dye are bound to one molecule of the antibody.
When the dye-labeled antibody is applied for an immunosensor, it is accordingly difficult to detect a target substance having a low concentration.